Magnetic disk drives have been used broadly as peripheral storage devices. As disk drives grow smaller, they are also becoming practical as a cost-effective replacement for solid state memory in a variety of electronic devices, e.g. cameras, fax machines, cellular phones, modems, pagers, handheld computing devices, printers, and copiers.
Magnetic disk drives and other peripheral devices are generally designed to meet one of a number of industry standard bus architectures to assure compatibility with a host system. These include, for example, the small computer serial interface (SCSI), serial storage architecture (SSA) and the integrated drive electronics (IDE) interface. Each type of peripheral bus architecture defines its own unique set of communication protocols. The host system, which may include a microprocessor, memory devices, and other circuits, communicates with these elements via a system bus. The system bus may comprise an industry standard architecture (ISA) bus, or a microchannel, for example. The system bus similarly has its own set of communications protocols. As such, the host system requires a device adapter to interface between the system bus and the peripheral bus.
An electronic circuit implementing a component-sized magnetic disk drive in lieu of solid state memory must also provide means for allowing the disk drive to communicate with the circuit application. Moreover, the circuit may be housed in a card enclosure and plugged into an application external to the circuit. It then requires means for interfacing with the external application.
For example, circuits embodying fax machines, modems, or disk drives, and circuits related to the operation of cellular phones and cameras are presently being housed in credit-card sized formats of predefined dimensions that plug into a compatible socket of a computing device. Three standard formats that have emerged for such credit-card-type applications are the PCMCIA formats. A "type III" card measures 10.5 mm in height, 85.6 mm in length and 54 mm in width. The dimensions of a "type II" card are approximately 5 mm high.times.85.6 mm long.times.54 mm wide. A "type I" card is a modest 3.3 mm high.times.85.6 mm long.times.54 mm wide. A PCMCIA card includes a PCMCIA bus for communicating with the computing device. Thus circuit applications residing in PCMCIA-type cards will include some type of interface to the PCMCIA bus.
Some electronic devices are incorporated into a communication network, e.g. via a phone line. These devices must conform to industry standard communications protocols such as asynchronous transfer mode (ATM), integrated services digital networks (ISDN), RS-232, RS-422, V.35, and V.42. Wireless communications devices such as cellular phones and electronic pagers must also be adapted to meet industry standard communications protocols. Computer peripherals such as printers and printed circuit cards similarly require means for interfacing to the host system. Each of these circuit application is a candidate for implementing a component disk drive in lieu of solid state memory, and as such, would require a customized interface between the disk drive and the application.
To add flexibility to an electronic device incorporating a component disk drive, it is desirable to include an adaptable interface within the device circuit, enabling it to conform to more than one communication or host system protocol. A number of U.S. patents discuss the use of an adaptable interface between two systems having different communications protocols. For example, U.S. Pat. No. 5,111,423 discloses a programmable interface, i.e. an EEPROM, inserted between a printed circuit card and a host system that is configurable for adapting a variety of printed circuit card applications to the same host system. U.S. Pat. No. 4,899,306 describes a test interface circuit having an adaptable interface, i.e. random access memory, for adapting the test circuit to different types of host systems. Another testing device with an adaptable interface comprising programmable gate arrays is described in U.S. Pat. No. 5,121,342. The testing device includes a microprocessor for receiving downloaded software from a removable floppy peripheral disk drive device and for selectively configuring the programmable gate arrays to a variety of communication protocols (e.g. RS-232, RS-422, V.35 and ISDN). U.S. Pat. No. 5,243,273 describes a testing device for serial communications cards that is configurable to a plurality of communications protocols.
However, to date, an electronic circuit apparatus has not been implemented that includes a component-level disk drive in lieu of solid state memory or an external floppy drive, and further comprises a programmable interface for adapting the electronic circuit to different types of communication protocols.